diff --git a/clang/lib/Basic/SourceManager.cpp b/clang/lib/Basic/SourceManager.cpp
--- a/clang/lib/Basic/SourceManager.cpp
+++ b/clang/lib/Basic/SourceManager.cpp
@@ -877,9 +877,12 @@
     I = (-LastID - 2) + 1;
 
   unsigned NumProbes;
+  bool Invalid = false;
   for (NumProbes = 0; NumProbes < 8; ++NumProbes, ++I) {
     // Make sure the entry is loaded!
-    const SrcMgr::SLocEntry &E = getLoadedSLocEntry(I);
+    const SrcMgr::SLocEntry &E = getLoadedSLocEntry(I, &Invalid);
+    if (Invalid)
+      return FileID(); // invalid entry.
     if (E.getOffset() <= SLocOffset) {
       FileID Res = FileID::get(-int(I) - 2);
       LastFileIDLookup = Res;
@@ -897,8 +900,8 @@
   while (true) {
     ++NumProbes;
     unsigned MiddleIndex = (LessIndex - GreaterIndex) / 2 + GreaterIndex;
-    const SrcMgr::SLocEntry &E = getLoadedSLocEntry(MiddleIndex);
-    if (E.getOffset() == 0)
+    const SrcMgr::SLocEntry &E = getLoadedSLocEntry(MiddleIndex, &Invalid);
+    if (Invalid)
       return FileID(); // invalid entry.
 
     ++NumProbes;